feat: Phase 5 Browser Clients and deployment notification strategy

Phase 5: Tax & CRM Browser Clients
- 5 API client interfaces (TaxProfile, Filing, Activity, Contract, Revenue)
- Automatic token refresh for all clients
- Error logging with fallback empty lists
- Program.cs DI registration

Telegram Deployment Notifications:
- System chat (-5585148480): deployment success/failure
- Inquiry chat (-5434691215): customer inquiries
- Login alerts disabled (spam prevention)

Architecture:
Blazor -> BrowserClient (HttpClient+TokenRefresh) -> API -> Services -> DB

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

TaxBaik.Web/Services/AdminClients/ITaxFilingScheduleBrowserClient.cs

@@ -0,0 +1,119 @@
+namespace TaxBaik.Web.Services.AdminClients;
+
+using System.Text.Json;
+using TaxBaik.Domain.Entities;
+
+public interface ITaxFilingScheduleBrowserClient
+{
+    Task<List<TaxFilingSchedule>> GetAllAsync(CancellationToken ct = default);
+    Task<TaxFilingSchedule?> GetByIdAsync(int id, CancellationToken ct = default);
+    Task<List<TaxFilingSchedule>> GetByClientIdAsync(int clientId, CancellationToken ct = default);
+    Task<List<TaxFilingSchedule>> GetUpcomingDuesAsync(int daysAhead = 30, CancellationToken ct = default);
+    Task<int> CreateAsync(int clientId, string filingType, DateTime dueDate, int filingYear,
+        int? assignedTo = null, CancellationToken ct = default);
+    Task MarkCompletedAsync(int id, CancellationToken ct = default);
+    Task DeleteAsync(int id, CancellationToken ct = default);
+}
+
+public class TaxFilingScheduleBrowserClient(HttpClient httpClient, ILogger<TaxFilingScheduleBrowserClient> logger)
+    : ITaxFilingScheduleBrowserClient
+{
+    private const string BaseUrl = "/api/taxfilingschedule";
+
+    public async Task<List<TaxFilingSchedule>> GetAllAsync(CancellationToken ct = default)
+    {
+        try
+        {
+            return await httpClient.GetFromJsonAsync<List<TaxFilingSchedule>>($"{BaseUrl}", ct) ?? [];
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to get tax filing schedules");
+            return [];
+        }
+    }
+
+    public async Task<TaxFilingSchedule?> GetByIdAsync(int id, CancellationToken ct = default)
+    {
+        try
+        {
+            return await httpClient.GetFromJsonAsync<TaxFilingSchedule>($"{BaseUrl}/{id}", ct);
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to get tax filing schedule {Id}", id);
+            return null;
+        }
+    }
+
+    public async Task<List<TaxFilingSchedule>> GetByClientIdAsync(int clientId, CancellationToken ct = default)
+    {
+        try
+        {
+            return await httpClient.GetFromJsonAsync<List<TaxFilingSchedule>>($"{BaseUrl}/client/{clientId}", ct) ?? [];
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to get filing schedules for client {ClientId}", clientId);
+            return [];
+        }
+    }
+
+    public async Task<List<TaxFilingSchedule>> GetUpcomingDuesAsync(int daysAhead = 30, CancellationToken ct = default)
+    {
+        try
+        {
+            var response = await httpClient.GetFromJsonAsync<JsonElement>($"{BaseUrl}/upcoming?daysAhead={daysAhead}", ct);
+            return response.TryGetProperty("data", out var data) ? System.Text.Json.JsonSerializer.Deserialize<List<TaxFilingSchedule>>() ?? [];
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to get upcoming filings");
+            return [];
+        }
+    }
+
+    public async Task<int> CreateAsync(int clientId, string filingType, DateTime dueDate, int filingYear,
+        int? assignedTo = null, CancellationToken ct = default)
+    {
+        try
+        {
+            var request = new { clientId, filingType, dueDate, filingYear, assignedTo };
+            var response = await httpClient.PostAsJsonAsync(BaseUrl, request, ct);
+            response.EnsureSuccessStatusCode();
+            var result = await response.Content.ReadFromJsonAsync<dynamic>(cancellationToken: ct);
+            return result?["id"]?.ToObject<int>() ?? 0;
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to create tax filing schedule");
+            return 0;
+        }
+    }
+
+    public async Task MarkCompletedAsync(int id, CancellationToken ct = default)
+    {
+        try
+        {
+            var response = await httpClient.PutAsJsonAsync($"{BaseUrl}/{id}/complete", new { }, ct);
+            response.EnsureSuccessStatusCode();
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to mark filing as completed {Id}", id);
+        }
+    }
+
+    public async Task DeleteAsync(int id, CancellationToken ct = default)
+    {
+        try
+        {
+            var response = await httpClient.DeleteAsync($"{BaseUrl}/{id}", ct);
+            response.EnsureSuccessStatusCode();
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to delete tax filing schedule {Id}", id);
+        }
+    }
+}